Electron discharge device and the method of assembly thereof



A 1944- c. T. GODDARD 2,355,432

ELECTRON DISCHARGE DEVIQEAND THE METHOD OF ASSEMBLY THEREOF Filed Aug. 4, 1942 2 Sheets-Sheet 1 INVENTOR (.TIGODDARD' BY amwim A TTORNEV Aug. 8, 1944. c. T. GODDARD 2,355,432

ELECTRON DISCHARGE DEVICE AND THE METHOD OF ASSEMBLY THEREOF 2 Sheets-Sheet 2 Filed Aug. 4, 1942 //v VEN ran a. T. GODDARD BY A T TORNEY Patented Aug. 8, 1944 ELECTRON DISCHARGE; pn yioii METHOD OF ASSEMBli Charles '1. Goddard, New,Yoi-k,'- N.-jl.,-;assigno 7 Western Electric Company, lncorporated York, N, Y., a corporationfof bleyv gorlr.

Application August-4, 1942;:seriar'Na 453514 This invention relates to electron dischargedevices and the method of assembly thereof, and more particularly to types of devices for use in high frequency transmission systems.

In the manufacture of such devices, the ac-- curate positioning of the various elements relative to each other is of utmost importance in order that the device when complete will produce the desired results.

Objects of the invention are to provide a simple and highly eificient electron discharge device and a method of assembling the same.

With these and other objects in view, the -invention comprises an electron discharge device and a method of assembling the same, the latter including steps through the aid of tools for locating and mounting a filament support with respect to a fixed part, locating a grid element relative thereto, adjusting the grid element through the aid of a dummy filament, and subsequently mounting the filament and otherelements.

Other objects and advantages will be apparent from the following detailed description when considered in conjunction with the accompany ing drawings, wherein Fig. 1 is a side elevational view partially insec tion of the lower shell and leads and illustrates the mounting of the lower filament support;

Fig. 2 is a top plan view of the structure shown in Fig. 1;

Fig. 3 is an enlarged fragmentary top plan view illustrating the positioning of the grid with respect to the lower filament support;

Fig. 4 is an enlarged vertical sectional view of the lower shell structure illustrating the upper filament support mounted and the dummy filament in place;

Fig. 5 is similar to Fig. 4, illustratingthe structure after the mounting of the filament;

Fig. 6 is a top plan view illustrating the mounting of the anode;

Fig. '7 is a fragmentary sectional view taken along the line -'l-'I of Fig. 8, and

Fig. 8 is a front elevational View of the completed device, portions thereof being broken away. j

Referring now to the drawings, attention is first directed to Fig. 1, which illustrates a lower shell ID of the contour shown, with various leads H, !2 l4 and I5. This structure thus fardescribed is preformed and is not considered as a step of the method but as a part of the complete structure. The first step of the method is the locating of a lower filament support I6. This support has a flattened endl'l inwhich a hole I3 is provided'for'tlie*filament, the oppositeend being supported "by; a bra'cket I9 of a contour adaptdto-"be disposed-upon thel'e'ad H. The support ['6 isdisposed-uponthe lead II at the desired height, ahdthr'oirgh the aid of a 'tool '20, the end- 11, particularly the hole I8 therein, is accuratelylocated a fixed distance from'the lead [2: Thetool IE-has an aperture 2ltherein,adjacent one end, adapted 'to'receive the lead 12 when the tool is positioned thereon, the other end of the tool being reduced-in width as shown, "to provide asurface- H- adaptedto be positioned in engagement-with the"=1'ea'dl5. When the'tool 20 is disposed in place; a pi'n'23t is'lowered through an aperture" Hyena: the filament support I6 is adjusted arcuately'abbut 'its lead ll until the pin 23' is'free to drop through :thehole I18. When this has been-accomplished, the support It may be fixed to 'its lead'*by suitable means such as welding,andthe' hole t8 will be fixed in its locabodimentithe grid'is of: the .fin type, including a mandrel 2! :about which portions of spiral convo-v lutidns. 2'8 Tof grid' wirezarei disposed. The mand'rel withg-the grid-J wire is partially embedded" in a-portion of abracket-29,-,another portion thereof being formed toreceiveand conform to lead l2. The' connectiori between the grid and its lead, at the" last mentioned portion, is such that thegrid willbe' heldby'friction in any desired position yetj may ibe-frotated on the ;-lead by the application? of suitable force. c 1

All of the elements including the filament supports'a-ndthe' filament, the 'grid and the anode are mounted with respect to one' object; namely the :lead l2.- In the previous step of :the method thelowerfilament sgupp rtglli, particularly the hole It} therein, wasaccuratelylocated by the aid of the-tool 20a-givemdistancezfrom the lead l2 and-at a definite position with respect to the lead.

1 1 The said given distance at which the hole [8 is locatedwith respect to the lead; I? i is also a I given dimension-of the grid 2 5,;this dimension being the distancebetweertvthe center of the'free convolution-portions-otthe grid wire and the center of the portionoflthe bracketwhich is disposed upon the lead? (2; This;dimension being known, the tool 20 is forme d accordingly to position the center of; the aperture 2! .a-givendistance from the aperture 24 which receives the. pin- 23 for 10 catingthe holel8. Thiisbylocating the bracket is of a block type structure made hollow at 32, with an arcuate contour at 33 to conform to the" adjacent portion of the bracket; 29 and withpar allel walls 34 to engage the adjacent'sidesof the grid bracket. Projections 35 of the tool terminating in a common plane with the center of the hole 18, when the grid is accurately positioned,

serve, in this instance, to aid in the location of the grid and serve subsequently in cooperation 3 r with adjacent surfaces 31 in the mounting of the anode, as will hereinafter be described.

With the tool 3! thus positioned as shown in- Fig. 3, the grid may bereadily movedabout its lead in either direction until it is centered with the hole [8 in the filament support. "The grid is not fixedto its lead at this" point in the method, but is held by itsfrictional engagement with the lead in its adjusted position so that a further adjustment mayv be'madeusubsequently in the assembling methodif suchadjustment is found necessary. a

Attention is now; directed to Fig. 4, whichile lustrates an-upperfilamentsupport similar in structure'to the forward or fiattenedend-Il of the support IS'and provided with'a hole or aper' ture4l therein. nThe support is mounted upon the free end of a resilient hook-shaped .wire 42 the opposite; end being-fixed to its lead 14' by suitable means such as welding. Suitable means (not shown) may be employed in locating the wire 42 adjacent the'lead l4 for the we ding or mounting operation. A dummy filament 44 may, if desired, be employed to locate the hole. in central alignment with the grid convolutions 28 and hole Win the lower filament support l5. This may b'e done during or afterthe mounting of'th'e upperfilament support 40. At this time an additional adjustment of thegrid maybe found necessary through the aid of the tool .31.. This adjustment of :the'upper filament support with respect to the grid and lower filamentsupport is a step important to assure accurate positioning of a filament 46 (Fig. when mounted in place. During all adjustments, it will 'be apparent that the entire grid, the filament supports and the dummy filament 44 maybe observed. The same is true during the mounting of the filament 46. 1 V i I When mounting the filament 46, it is important that the wire 42 upon whichtheupper filament support 40 is mounted,-is flexed a' given distance to assure predetermined tension on the filament after it has-been mounted; This may be accomplished by a tool 47. The filament 45 is'then disposed in place by passing it downwardly through the hole 4|, through the convolutions 28 of the grid,'through the hole [8 in the lower support 16, and allowed to rest upon the surface of the shelljlll, Thusflthe filament when first disposed in place asdescribed, is of excess length, the excess'portions being subsequently removed after the welding of the filament to its supports, these excess lengths being shown in dot and dash lines in Fig. 5; Thetool 41 having hooked ends 48 and 49 adapted to extend around the lower and upper filament supports, 01 $119 specifically the bracket l9 and the wire 42, serves to hold the wire 42 flexed the desired distance. The filament 45 is then secured in place by suitable means such as arc welding. The tool 41 is left in place until after the welding operation and until the associated parts adjacent the welds have had time to cool At this time the tool may be removed-by sliding? it in 'a"direction to free it of the bracket l9, this'being done with- ,out disturbing the wire 42 or the filament 46.

' At this time during the method of assembly, anothencheck is made on the alignment of the filament andgrid. This is important due to the fact thatthe filament may not be in the same location afterthewelding as before, this being due to the possible travel of the filament during the welding operation. Furthermore, due to the application of thewelds from the same direction fromthe left (Fig. 5) and to the ends of 20 the supports it and 48, the travel, if any, of the endsof the filament would be in the same direction. ."Although there is but little clearancebetween'the filament. and'jthe walls of the holes [8 and 4i, the material of the filament and'its supports may flow when softenedduringthe welding- 'operation, and with this'possibility in mind,': a further checkingof the grid and its location with respect to" the filament is essential.

By applying the welding means 'at'the ends of .the' filament supports and ma direction toward the filament and the leads of the respective supports, the travel, if any, of the ends of the filament-willbe transverse to the general plane of the'grid so that further adjustment of thegr-id through its arcuate movement about its lead l2, may be made to again create an alignment of the center line of'the gridgnamely the center line'- of'the'arcuate endsof the grid convolutions, W i'th 'the filament When this has been accompIished -the grid maybe secured in place on its lead by'suitable means such as welding. The 'next step includes the mounting of an anode, indicated at 5B, which in the pre'sentembodi'ment is formed of two like portions abutting each other at 5|, where they are secured together by punched out portions 52,'other portions 53 extending arcuately away from 'each other to form 'a'n' arc,'the center of which is at the filament 46"andthe center of'the grid convolutions 28. Continuing with the formation of the portions of the anode, it will be observed that they extend outwardlyin a common plane as at 54, their ends projecting diagonally therefrom at like angles as indicated at 55. I Beneath thefportions 5| and integral therewith, are like portions 55 which extend in spaced parallel planes, as shown, adapted to be positioned upon each side of their lead I5. In actual structure the portions 56 are spaced apart a greater distance than the diameter of the lead l5 and are also of greater length than this dimension of the lead, as shown in Fig. '7, toallow for adjustment or location of the anode at various positions with respect to its lead, depending upon'the' final location of the grid and filament. With this structure of the anode, it may be moved in a horizontal plane (Fig. 6) into the position shown'in 'this figure, its'final' position being governed by the tool'3l. At this step in the method, the tool can no longer be moved arcuately about the lead l2, as the grid hasbeen fixed to its lead. Therefore, when the anode has been disposed in the position shown, with the projections 35 positionedwithin the anodeand theportions 4 9f the latter'resting against the surfaces 31 of the tool, the anode is accurately located with the center of the portion 53 thereof at the'center of the filament 46 and grid convolutions 28. When in this position the portions 55 of the anode will lie upon each side of the lead [5, and while the anode is thus held in place against the tool 3 i, the portions 56 may be secured to the lead i5 by suitable means, such as spot welding. The tool 3| may then be removed by moving are the left (Fig. 6), to move the opposite ends free of the anode and of the filament supports, after which it may be moved upwardly or laterally free of the grid. Finally, an upper shellfiii may be disposed upon and fused to the loWer'shell Iii, evacuated in the usual manner, and sealed to complete the formation of the device.

In reviewing the step of the method, it will b apparent that all of the elements have been located accurately with respect to one object, namely the lead I2. During the preforming of the shell I ll with the leads therein, this structure may be presumed to have the leads disposed at accurately spaced positions, but due to the fact that the elements supported by the leads must be mounted so that the filament, the arcuate ends of the grid convolutions and the arcuate portion of the anode will have a common center, it has been found advantageous not to depend upon the accuracy in which the leads are mounted in their shell, but the mounting of the'elements from a given object. It is with this thought in mind that the lower filament support or the hole I 8 therein, is located a known distance from the selected obiect, namely the lead l2, this known distance be. ing the distance between the mounting center and the convolution center of the grid which will 10- cate the latter the same distance from the object or lead l2. Thus through arcuate adjustment of the grid, these centers may be aligned. Furthermore, the tool 3| with its arcuate recesses 33 formed to allow for the thickness of the bracket portion disposed upon the lead l2, performs its functions about the leadin not only adjusting the grid but in locating the anode with respect thereto, Here again the tool functions, through the aid of the projection 35 and the surfaces 37, to locate the center of the anode, namely the center of the arcuate portion 53 at the center of the filament and the grid convolutions. As a result thereof, the maximum efficiency of the elements may be obtained. i

Although specific improvements of the inven tion have been shownand described, it will-.be understood that they are but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined by the appended claims.

What is claimed is: 1. The method of assemblingan electron discharge device having a vessel of two shell Sections, one provided with spaced-leads, the method the said center, securing a filament to the said portions, mounting an anode on its lead. and coinpleting the device by sealing the shells together and evacuating them.

2. The method ofassembling an electron [disand evacuating them.

charge device having a vessel of tWo'shell sections, one provided withspaced leads, the method comprising mounting a filament support with a filament receiving portion on its respective lead with the said portion a given distance from the lead for a-grid having agrid wire formed arcuately about a center, positioning the grid on its lead, adjusting thegrid arcuately about its lead until the center-thereof is aligned with the said portion orthe'filament support; mounting another filament/support on its lead with a filament receiving portion thereof disposed in alignment with the said center, securing a filament'to the said portions, mounting an anode on'its lead, and com.- pleting the deviceby sealing the shells together 3. The method of assembling an electron'discharge device having a vessel'of two shell sections, one provided with spaced leads, the method comprising mounting a filament support with a filament receiving portion on its respective lead with the said portion a given distance from the lead for a grid having a grid Wire formed arcuate- 1y about a center, positioning the grid on its lead, aligning the grid center with the said portion of the filament support, mounting another filament support on its lead with a filament receiving'pore tion thereof disposed in alignment with the said center, securing a filament to the said portions, mounting an anode, having aportion arcuate about a center, with the said center at the grid center, and completing the device by sealing the shells together and evacuating them.

4. The method of assembling an electron discharge device having a vessel of two shell sections;one provided with spaced leads, the method comprising mountinga filament support with a filament'receivingv portion on its respective lead with the said portion a given distance from the lead for a grid having a grid wire formed arcuately about a center, positioning the grid on its lead, aligning the grid center with the-said portion of the filament support, mounting-another filament support on its lead'with a filament receiving portion thereof disposed in alignment with the said center, securing a filament to the said portions, mounting an anode a given distance from the grid lead,"and completing the device by sealing the shells together and evacuating them.

5. The method of assembling an electron discharge device having a vessel of two'sections, one provided with spaced leads, the .method comprising successively locating filament supports, a grid and an'anode: on their respective leads and adjusting them, the filament supports, the .grid and. the anode, relative to a predetermined one of the leads, securing a filament to the supports, and completing the device by sealing the sections together and evacuating them; 1

6;The method of assembling an electron discharge device having a vessel of two sections, one provided with spaced leads, the method comprising successively locating filament supports, a grid and an anode'on their respective leads and adjusting them, the filament supports; the grid and the anode, relative to a predetermined one of the leads, securing a filament to thesupportsprior to the locatingand adjustment of 'the anode,'and completing the device by sealing the sections together and evacuating them; r

7. The method of assembling an electron discharge device having a vessel of two shell sections, one provided with spaced leads, the method comprising successively locating filament supports, a grid and an anode on their respective leads and adjusting them relative to a predetermined one of the leads, welding a filament to the supports prior to the locating and adjustment of the anode, adjusting the grid relative to the filament to compensate for travel of the filament when being welded, and completing the device by sealing the shells together and evacuating them.

8. The method of assembling an electron discharge device having a vessel of two shell sections, one provided with spaced leads, the method comprising successively locating filament supports, a grid and an anode on their respective leads and adjusting themrelative to a predetermined one of the leads, securing a filament to the supports prior to the locating and adjust ment of the anode, holding one of the supports in a flexed position during welding of the filament, and completing the device by sealing the shells together and evacuating them.

9. The method of assembling an electron discharge device having a vessel of two shell sections, one provided with spaced leads, the method comprising successively locating filament supports, a grid and ananode on their respective leads and adjusting them relative to a predetermined one of the leads, employing a dummy filament between the supports during the relative adjustments of the grid and supports, securing a filament to the supports prior to the locating and adjustment of the anode, and completing the device by sealing the shells together and evacuating them.

10. An electron discharge device comprising a hollow vessel of two shell sections, one provided with spaced leads for a grid, an' anode and filament supports, a filament support, having a filament receiving portion, mounted on its lead with the said portion disposed ag'iven distance from the grid lead, a grid mounted upon'its lead and .having a grid wire formed arcuately about a center spaced the said given distance from the grid lead and in alignment with the said portion, another filament support, having a filament receiving portion, mounted upon its lead with its portion in alignment with the said center and other portion, a filament secured to the portions of the supports, and an anode mounted upon its lead.

11. An electron discharge device comprising a hollow vessel of two shell sections, one provided with spaced leads for a grid, an anode and filament supports, a filament support, having a filament receiving portion, mounted on its lead with the said portion disposed a given distance from the grid lead, a grid having a body, apertured for mounting on its lead, supporting a grid wire formed arcuately about a center spaced the given distances from the lead disposed with the said center in alignment with the said portion, another filament support, having a filament receiving portion, mounted upon its lead with its portion in alignment with the said center and other portion, a filament secured to the portions of the supports, and an anode mounted upon its lead;

12. An electron discharge device comprising a hollow vessel of two shell sections, one provided with spaced leads for a grid, an anode and filament supports, a filament support, having a filament receiving portion, mounted on its lead with the said portion disposed a given distance from the grid lead, a grid having a body, apertured longitudinally thereof for mounting on its lead, supporting a grid wire formed arcuately about a center spaced the given distances from the lead disposed with the said center in alignment with the said portion, another filament support, having a filament receiving portion, mounted upon its lead with its portion in alignment with the said center and other portion, a filament secured to the portions of the supports, and an anode mounted upon its lead.

13. An electron discharge device comprising a hollow vessel of two shell sections, one provided with spaced leads for a grid, an anode and filament supports, a grid having a body, with a longitudinal aperture therein to receive its lead for pivotal adjustable mounting thereon relative to the other leads, and supporting a grid wire with convolutions formed arcuately about a center line spaced a given distance from the lead, filament supports mounted upon their leads and having filament receiving portions disposed in alignment with the said center line, a filament mounted upon the supports at the center line, and an anode mounted upon its lead.

14. An electron discharge device comprising a hollow vessel of twoshell sections, one provided with spaced leads-for a grid, an anode and filament supports, a filament support, having a filament receiving portion, mounted on its lead with the said portion disposed a given distance from the grid lead, a grid mounted upon its lead, having a grid wire formed arcuately about a center spaced the said given distance from the grid lead and movable arcuately about its lead to align the said center with the said portion, another filament support, having a filament receiving portion, mounted upon its lead with its portion in alignment with the said center and other portion, a filament secured to the portions of the supports, an anode having a portion formed arcuately about a center and portions adapted to straddle its lead for movement of the anode relative to its lead to position its center at the grid center, and means to secure the portions to their lead.

15." An electron discharge device comprising a hollow vesselof two shell sections, one provided with spaced leads for a grid, an'anode and filament supports, a filament support, having a filament receiving portion, mounted on its lead with the said portion disposed a given distance from the grid lead, a grid mounted upon its lead, having a grid wire formed arcuately about a center spaced the said given distance from the grid lead and movable arcuately about its lead to align the said center with the said portion, another filament support, having a filament receiving por tion, mounted upon its lead with its portion in alignment with the said center and otherportion, a filament secured to the portions of the supports, an anode formed of connected similar sections providing portions formed arcuately about a center and other portions adapted to straddle its lead for movement into location with its center at the grid center, and means to secure the last mentioned portions together.

16. In the manufacture of an electron discharge device involving a vessel of precast shell sections, one provided with spaced leads for a grid, an anod and filament supports, the method which comprises positioning a filament support with a filament receiving portion on its respective lead, placing a locating member on the grid lead and throughthe aid thereof locating the said portion a given distance from the grid lead, removing the locating member, positioning a grid, having a grid wire formed arcuately about a center, on its lead, positioning a tool on the grid to move the grid thereby and align the center thereof with the said portiommounting a'filament at the portion, locating an anode adjacent the gridbythe tool, securing the anode to its lead, removing the tool and completing the device by sealing the shell sections together and evacuating-them.

17. In the manufacture of an electron discharge device involving a vessel of precast sections, one provided with leads for a grid, an anode and filament supports, the method which comprisespositioning a filament support with a filament receiving portion on its respective lead, placing a locating member on the grid lead and through the aid thereof locating the said portion a given distance from the grid lead, removing the locating member, positioning a grid, having a grid wire formed arcuately about a center, on its lead with the said center in alignment with the said portion, mounting another filament support, having a filament receiving portion, with its portion in alignment with the said center and other portion, mounting a filament at the portions, mounting an anode on its lead adjacent the grid, and completing the device by sealing the sections together.

18. In the manufacture of an electron discharge device involving a vessel of precast sections, one provided with leads for a grid, an anod and filament supports, the method which comprises positioning a filament support with a filament receiving portion on its respective lead with the said portion located a given distance from the grid support, positioning a grid having a body formed for pivotal mounting on its lead and to support grid wire formed arcuately about a center, positioning a tool on the grid to move the grid thereby about its lead to align the center thereof with the portion, removing the tool, mounting another filament support, having a filament receiving portion, with its portion in alignment with the said center and other portion, mounting a filament at the portions, mounting an anode on its lead adjacent the grid, and completing the device by sealing the sections together.

19. In the manufacture of an electron discharge device involving a vessel of precast sections, one provided with leads for a grid, an anode and filament supports, the method which comprises positioning a filament support with a filament receiving portion on its respective lead with the said portion located a given distance from the grid support, positioning a grid having a body formed for pivotal mounting on its lead and to support grid wire formed arcuately about a center, positioning a tool on the grid to move the grid thereby about its lead to align the center thereof with the portion, mounting another filament support, having a filament receiving portion, with its portion in alignment with the said center and other portion, locating an anode on its lead adjacent the grid by the tool, securing the anode to its lead, removing the tool, and completing the device by sealing the sections together.

20. In the manufacture of an electron discharge device involving a vessel of precast sections, one provided with leads for a grid, an anode and filament supports, the method which comprises positioning a filament support with a filament receiving portion on its respective lead with the said portion located a given distance from the grid support, positioning a grid, having a grid wire formed arcuately about a center, on its lead with the said center in alignment with the said .portion, mounting a resilient filament support having a; filamentreceiving portion with its portion in general alignment with the said center and other portion, flexing the resilient support toward the other support to position the portions a given distance from eachfother, mounting a filament at the portions, mountingan anode on its leadadjacentthegrid, and. cgmpleting the device by sealing the sections together.

, 21. In the manufacture of ,an electron discharge deviceinvolying a vessel of precast sections, one provided with leads for a grid, an anode and filament sup "rts, the method which comprises positioning ment receiving port on on its respective lead with the said portion loci ted a given distance from the grid support, positioning a grid, having a grid wire formed arcuately about a center, on its lead with the said center in alignment with the said portion, mounting-la resilient filament support having a filament receiving portion with its portion in general aligriment with the said center and other portion, flexing the resilient support toward the other support tQ position the portions a given distance from each'fother, connecting the filament supports with a holding member to maintain the given distance of the portions, mounting a filament at the portions, removing the holding member, mounting an anode on its lead adjacent the grid, and completing the device by sealing the sections togethen;

22. In the manufacture of an electron discharge device involving a vessel of precast sections, one providedgwith leads for a grid, an anode and filament supports, the method which comprises positioning a filament support with a filament receiving portion on its respective lead, placing a locating-{member on the grid lead and through the aid thereof locating the said portion a given distance from the grid lead, removing the locating member, positioning a grid having a body formed for pivotal mounting on its lead and to support grid wire formed arcuately about a center, positioning a to0l;on the grid to move the grid thereby about its lead to align the center thereof with the portion, mounting another filament support, having a filament receiving portion, with its portion in alignment with the said center and other portion, removing the tool, mounting an anode on its lead adjacent the grid, and completing the device by sealing the sections together.

23. In the manufacture of an electron discharge device involving a vessel of precast sections, one providedwith leads for a grid, an anode and filament supports, the method which comprises positioningia filament support with a filament receiving portion on its respective lead, placing a locating member on the grid lead and through the aid thereof locating the said portion a given distance fromthe grid lead, removing the locating member, positioning a grid having a body formed for pivotal mounting on its lead and to support grid wire formed arcuately about a center, positioning a tool on the grid to move the grid thereby about its lead to align the center thereof with the portion, mounting another filament support, having a filament receiving portion, with its portion in alignment with the said center and other portion, locating an anode on its lead adjacent the grid by the tool, securing the anode to its lead, removing the tool, and completing the device by sealing the sections together.

24. In the manufacture of an electron discharge device involving a vessel of precast sections, one provided with leads for a grid, an anode and filament supports, the method which comprises positioning a filament support with a filament receiving portion on its respective lead with the said portion located a given distance from the grid support, positioning a grid having a body formed for pivotal mounting on its lead and to support 'grid wire formed arcuately about acenter, positioning a tool on the grid to move the grid thereby about its lead to align the center thereof with the portion, mounting another filament support,

having a filament receiving portion, with its por- CHARLES T. GODDARD. 

